Silicon-based ammonia cracking hydrogen production catalyst and preparation method and application thereof

Abstract

The present application relates to the field of catalysts, and specifically, provides a silicon-based ammonia cracking hydrogen production catalyst and its preparation method and application. The silicon-based ammonia cracking hydrogen production catalyst includes a silicon-based carrier, an active component and a modification aid; the silicon-based carrier includes silicon nitride, silicon carbide, silicon molybdenum powder, diatomaceous earth, pure silicon molecular sieve, silicon dioxide or SAB-16; the active component includes at least one of Ru, Co, Mo, and Fe; the modification aid includes at least one of Li, Na, K, Cs, Rb, Ba, and Ir. The catalyst of the present application is 12000mL·g ‑1 ·h ‑1 , the NH3 conversion rate exceeds 80% under 500℃ conditions, and basically no by-products are produced; it effectively solves the problem of hydrogen embrittlement of traditional ammonia cracking material carriers; it also has high oxidation resistance and does not react with oxygen in a dry atmosphere below 800℃.

Description

Technical Field

[0001] The present application relates to the field of catalysts, and in particular, to a silicon-based ammonia cracking hydrogen production catalyst and a preparation method and application thereof. Background Art

[0002] Hydrogen is regarded as the most ideal clean energy, and its research and practice in the automotive field are in full swing. In the future, hydrogen-powered vehicles are believed to be expected to become a new vehicle power source, especially for heavy trucks. However, due to the limitations of the molecular physical and chemical properties, the storage, transportation and application of hydrogen pose great safety risks. Using ammonia, which has stable properties, wide sources and mature industry, as a hydrogen storage carrier is one of the technical approaches to solve the bottleneck of large-scale application of hydrogen energy in recent years. The ammonia cracking reaction to produce hydrogen is an endothermic reaction, which usually needs to be carried out at a higher temperature. The current catalysts are still insufficient in lowering the reaction temperature and reducing hydrogen embrittlement.

[0003] In view of this, this application is hereby filed. Summary of the invention

[0004] The purpose of the present application is to provide a silicon-based ammonia cracking hydrogen production catalyst and a preparation method and application thereof, so as to solve the problems of high catalytic reaction temperature and easy hydrogen embrittlement in the prior art.

[0005] In order to achieve the above-mentioned purpose of this application, the following technical solutions are specially adopted:

[0006] In a first aspect, the present application provides a silicon-based ammonia cracking hydrogen production catalyst, comprising a silicon-based carrier, an active component and a modification aid;

[0007] The silicon-based carrier includes silicon nitride, silicon carbide, silicon molybdenum powder, diatomaceous earth, pure silicon molecular sieve, silicon dioxide or SAB-16;

[0008] The active component includes at least one of Ru, Co, Mo and Fe;

[0009] The modification aid includes at least one of Li, Na, K, Cs, Rb, Ba, and Ir.

[0010] As a further preferred technical solution, the loading amount of the active component is 1wt%~10wt%.

[0011] As a further preferred technical solution, the loading amount of the modification aid is 0.2wt%~5wt%.

[0012] In a second aspect, the present application provides a method for preparing the above-mentioned silicon-based ammonia cracking hydrogen production catalyst, comprising the following steps:

[0013] Dissolving the precursor of the active component in water, then adding the precursor of the modifying auxiliary agent, and dispersing by ultrasonication to obtain a first solution;

[0014] The first solution is mixed with a silicon-based carrier, heated and stirred, and then dried and calcined to obtain the catalyst.

[0015] As a further preferred technical solution, the ultrasonic dispersion time is 0.5 to 1.5 h.

[0016] As a further preferred technical solution, the heating and stirring temperature is 60°C to 180°C, and the stirring time is 2 to 10 hours.

[0017] As a further preferred technical solution, the drying temperature is 40-120° C., and the drying time is 10-14 hours.

[0018] As a further preferred technical solution, the calcination atmosphere is an ammonia atmosphere, the calcination temperature is 450-550° C., and the calcination time is 2-6 hours.

[0019] In a third aspect, the present application provides an application of the above-mentioned silicon-based ammonia cracking hydrogen production catalyst or the silicon-based ammonia cracking hydrogen production catalyst prepared by the above-mentioned preparation method in ammonia cracking hydrogen production.

[0020] Compared with the prior art, the beneficial effects of this application are:

[0021] The silicon-based ammonia cracking hydrogen production catalyst provided in the present application comprises a specific silicon-based carrier, a specific active component and a specific modification auxiliary agent. The silicon-based carrier has a high specific surface area. By loading the active component and the modification auxiliary agent, the catalytic reaction temperature of ammonia cracking hydrogen production can be effectively reduced, and the H 2 Yield and catalyst life, at 12000mL·g -1 ·h -1 , NH at 500℃ 3 The conversion rate exceeds 80%, and basically no by-products are produced; the carrier does not contain metal elements, which effectively solves the problem of hydrogen embrittlement of traditional metal carriers; the silicon-based carrier can provide good thermal stability, which is especially important for high-temperature reactions such as ammonia cracking. At high temperatures, the stability of the catalyst directly affects the life of the catalyst and the sustainability of the reaction. In addition, it has high oxidation resistance and does not react with oxygen in a dry atmosphere below 800°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the SEM image of the silicon-based ammonia cracking hydrogen production catalyst in Example 8 Figure 1 ;

[0023] Figure 2 This is the SEM image of the silicon-based ammonia cracking hydrogen production catalyst in Example 8 Figure 2 . DETAILED DESCRIPTION

[0024] The embodiments of the present application will be described in detail below in conjunction with the examples, but those skilled in the art will understand that the following examples are only used to illustrate the present application and should not be considered to limit the scope of the present application. If no specific conditions are specified in the examples, they are carried out according to conventional conditions or conditions recommended by the manufacturer.

[0025] According to one aspect of the present application, the present application provides a silicon-based ammonia cracking hydrogen production catalyst, including a silicon-based carrier, an active component and a modification aid;

[0026] The silicon-based carrier includes silicon nitride, silicon carbide, silicon molybdenum powder, diatomaceous earth, pure silicon molecular sieve, silicon dioxide or SAB-16;

[0027] The active component includes at least one of Ru, Co, Mo and Fe;

[0028] The modification aid includes at least one of Li, Na, K, Cs, Rb, Ba, and Ir.

[0029] Among them, silicon-molybdenum powder refers to a mixed powder of silicon and molybdenum. Pure silicon molecular sieve refers to a molecular sieve composed only of silicon. SAB-16 is a mesoporous material and belongs to the SBA (Santa Barbara Amorphous) series of materials. These materials usually have a regular pore structure, a high specific surface area, and good thermal and chemical stability, which makes them widely used in catalysis, adsorption and separation. The characteristics of SAB-16 material include a cubic phase structure, which is conducive to the rapid diffusion of reactive molecules, and abundant silicon hydroxyl groups, which can be surface modified by silanization reaction to adjust its surface properties and functions.

[0030] The active components in the present application include but are not limited to: Ru, Co, Mo, Fe, Ru and Co, Co and Mo, Mo and Fe, Mo and Ru, Ru and Fe, Ru, Co and Fe, Co, Mo and Fe, or Ru, Co, Mo and Fe, etc.

[0031] The modification aids in the present application include but are not limited to: Li, Na, K, Cs, Rb, Ba, Ir, Li and Na, Na and K, K and Cs, Cs and Rb, Li, Na and K, K, Cs and Rb, Cs, Rb and Ba, Rb, Ba and Ir, Li, Na, K and Cs, Na, K, Cs and Rb, Cs, Rb, Ba and Ir, Li, Na, K, Cs and Rb, K, Cs, Rb, Ba and Ir, Li, Na, K, Cs and Rb, K, Cs, Rb, Ba and Ir, Li, Na, K, Cs, Rb and Ba, Na, K, Cs, Rb, Ba and Ir, or Li, Na, K, Cs, Rb, Ba and Ir, etc.

[0032] The silicon-based ammonia cracking hydrogen production catalyst comprises a specific silicon-based carrier, a specific active component and a specific modification agent. The silicon-based carrier has a high specific surface area. By loading the active component and the modification agent, the catalytic reaction temperature of ammonia cracking hydrogen production can be effectively reduced, and the H 2 Yield and catalyst life, at 12000mL·g -1 ·h -1 , NH at 500℃ 3 The conversion rate exceeds 80%, and basically no by-products are generated; it effectively solves the problem of hydrogen embrittlement of traditional ammonia cracking material carriers; it also has high oxidation resistance and does not react with oxygen in a dry atmosphere below 800°C.

[0033] In an optional embodiment, the loading amount of the active component is 1wt%~10wt%. The loading amount of the above active component includes but is not limited to 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt% or 10wt%. It has been proved by experiments that when the loading amount of the active component is within the above range, the comprehensive performance of the obtained catalyst is better. The loading amount of the active component affects the performance of the catalyst by adjusting the dispersion of the metal elements and the intervals between the metal elements.

[0034] In an optional embodiment, the loading amount of the modification aid is 0.2wt%~5wt%. The loading amount of the above-mentioned modification aid includes but is not limited to 0.2wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt% or 5wt%. The modification aid can change the electronic properties of the catalyst, thereby adjusting the performance of the catalyst. Preferably, the loading amount of the modification aid is 4wt%~5wt%.

[0035] It should be noted that the loading amount in the present application refers to the weight percentage of the active component or the modification aid in the silicon-based carrier.

[0036] According to another aspect of the present application, the present application provides a method for preparing the above-mentioned silicon-based ammonia cracking hydrogen production catalyst, comprising the following steps:

[0037] Dissolving the precursor of the active component in water, then adding the precursor of the modifying auxiliary agent, and dispersing by ultrasonication to obtain a first solution;

[0038] The first solution is mixed with a silicon-based carrier, heated and stirred, and then dried and calcined to obtain the catalyst.

[0039] The method is used to prepare the aforementioned silicon-based ammonia cracking hydrogen production catalyst, has a simple preparation process, low cost, and is easy to promote. The prepared silicon-based ammonia cracking hydrogen production catalyst has good catalytic performance.

[0040] Optionally, the precursor of the active component and the precursor of the modification aid are independently soluble salts thereof, such as halides and the like.

[0041] In an optional embodiment, the ultrasonic dispersion time is 0.5 to 1.5 hours. The ultrasonic dispersion time includes but is not limited to 0.5 hours, 1 hour or 1.5 hours. Ultrasonic dispersion treatment mainly improves the dispersibility of active components and modification aids. The ultrasonic time is generally selected to be 0.5-1 hour. Further increasing the ultrasonic time has little effect on the catalyst performance.

[0042] In an optional embodiment, the temperature of the heating and stirring is 60°C to 180°C, and the stirring time is 2 to 10 hours. The above-mentioned heating and stirring temperature includes but is not limited to 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C or 180°C. The above-mentioned stirring time includes but is not limited to 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h. The stirring temperature mainly makes the catalyst mix more evenly, and increasing the temperature can make the reaction complete faster; the longer the stirring time is theoretically, the better, but considering the time cost, generally 2 to 10h is selected, preferably 3 to 6h.

[0043] In an optional embodiment, the drying temperature is 40-120°C and the drying time is 10-14h. The above drying temperature includes but is not limited to 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C or 120°C. The above drying time includes but is not limited to 10h, 11h, 12h, 13h or 14h. The lower the drying temperature, the better, but the drying time will increase; if the drying temperature is too high, the evaporation rate of water will be faster, which will drive the active components and modification aids to migrate to the catalyst surface, which is not conducive to the dispersion of the active components and modification aids. The drying temperature is generally selected from 40 to 120°C, preferably 80 to 100°C.

[0044] Optionally, before the drying, the process further includes filtering and washing 3 to 5 times to remove impurities and increase the proportion of the target substance.

[0045] In an optional embodiment, the calcination atmosphere is an ammonia atmosphere, the calcination temperature is 450-550°C, and the calcination time is 2-6h. The above calcination temperature includes but is not limited to 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C or 550°C. The above calcination time includes but is not limited to 2h, 3h, 4h, 5h or 6h. If the calcination temperature is too low, the desired compound cannot be formed, and if the temperature is too high, the catalyst may sinter or the active component may volatilize. Generally, 450-550°C is selected, preferably 500-550°C, and the best is 500°C.

[0046] According to another aspect of the present application, the present application also provides an application of the above silicon-based ammonia cracking hydrogen production catalyst or the silicon-based ammonia cracking hydrogen production catalyst prepared by the above preparation method in ammonia cracking hydrogen production. The application of the above silicon-based ammonia cracking hydrogen production catalyst in ammonia cracking hydrogen production can significantly reduce the reaction temperature, reduce energy consumption, reduce the generation of by-products, and avoid the problem of hydrogen embrittlement.

[0047] The present application is further described in detail below with reference to embodiments and comparative examples.

[0048] Example 1

[0049] A silicon-based ammonia cracking hydrogen production catalyst, comprising a silicon-based carrier, an active component and a modification aid;

[0050] The silicon-based carrier is silicon nitride; the active component is Ru; and the modification aid is Li.

[0051] The loading amount of active components is 12wt%, and the loading amount of modification aid is 6wt%.

[0052] The above silicon-based ammonia cracking hydrogen production catalyst is prepared by the following method: the precursor of the active component, the precursor of the modification aid, water and the silicon-based carrier are mixed together, and then dried and calcined after heating and stirring to obtain the catalyst. The heating and stirring temperature is 90°C and the stirring time is 10h; the drying temperature is 100°C and the drying time is 12h; the calcination atmosphere is an ammonia atmosphere, the calcination temperature is 500°C and the calcination time is 5h.

[0053] Embodiment 2-4

[0054] A silicon-based ammonia cracking catalyst for hydrogen production. The difference from Example 1 is that the loading amounts of the active components in Examples 2-4 are 1wt%, 5wt%, and 10wt%, respectively, and the rest are the same as Example 1.

[0055] Embodiment 5-7

[0056] A silicon-based ammonia cracking catalyst for hydrogen production. The difference from Example 4 is that the loading amounts of the modification aids in Examples 5-7 are 0.2wt%, 3wt%, and 5wt%, respectively, and the rest are the same as Example 4.

[0057] Example 8

[0058] A silicon-based ammonia cracking hydrogen production catalyst, which is different from Example 7 in that the catalyst in this example is prepared by: dissolving the precursor of the active component in water, then adding the precursor of the modification aid, and ultrasonically dispersing to obtain a first solution; mixing the first solution with a silicon-based carrier, heating and stirring, drying and calcining to obtain the catalyst. The ultrasonic dispersion time is 1 hour. The rest is the same as Example 7.

[0059] Examples 9-12

[0060] A silicon-based ammonia cracking hydrogen production catalyst, which is different from Example 8 in that the ultrasonic dispersion time in Examples 9-12 is 0.2h, 0.5h, 1.5h, and 2h, respectively. The rest is the same as Example 8.

[0061] Embodiment 13

[0062] A silicon-based ammonia cracking hydrogen production catalyst, which is different from Example 8 in that the heating and stirring temperature in this example is 60° C. and the stirring time is 10 hours. The rest is the same as Example 8.

[0063] Embodiment 14

[0064] A silicon-based ammonia cracking hydrogen production catalyst, which is different from Example 8 in that the heating and stirring temperature in this embodiment is 180° C. and the stirring time is 2 hours. The rest is the same as Example 8.

[0065] Embodiment 15

[0066] A silicon-based ammonia cracking hydrogen production catalyst, which is different from Example 8 in that the drying temperature in this example is 40° C. and the drying time is 14 hours. The rest is the same as Example 8.

[0067] Example 16

[0068] A silicon-based ammonia cracking hydrogen production catalyst, which is different from Example 8 in that the drying temperature in this example is 120° C. and the drying time is 10 hours. The rest is the same as Example 8.

[0069] Embodiment 17

[0070] A silicon-based ammonia cracking hydrogen production catalyst, which is different from Example 8 in that the calcination temperature in this example is 450° C. and the calcination time is 6 hours. The rest is the same as Example 8.

[0071] Embodiment 18

[0072] A silicon-based ammonia cracking hydrogen production catalyst, which is different from Example 8 in that the calcination temperature in this example is 550° C. and the calcination time is 2 h. The rest is the same as Example 8.

[0073] Embodiment 19

[0074] A silicon-based ammonia cracking hydrogen production catalyst, which is different from Example 8 in that the silicon-based carrier in this example is silicon-molybdenum powder, the active component is Co, and the modification aid is Cs. The rest is the same as Example 8.

[0075] Embodiment 20

[0076] A silicon-based ammonia cracking hydrogen production catalyst, which is different from Example 8 in that the silicon-based carrier in this example is pure silicon molecular sieve, the active component is Fe, and the modification aid is Ir. The rest is the same as Example 8.

[0077] Embodiment 21

[0078] A silicon-based ammonia cracking hydrogen production catalyst, which is different from Example 8 in that the silicon-based carrier in this example is silicon dioxide, the active components are Ru and Co (weight ratio is 1:1), and the modification aids are K and Rb (weight ratio is 1:1). The rest is the same as Example 8.

[0079] Embodiment 22

[0080] A silicon-based ammonia cracking hydrogen production catalyst, which is different from Example 8 in that the silicon-based carrier in this example is silicon carbide, the active components are Co, Mo and Fe (weight ratio is 1:1:1), and the modification aids are Na, Ba and Ir (weight ratio is 1:1:1). The rest is the same as Example 8.

[0081] Figure 1-Figure 2 This is a SEM image of the silicon-based ammonia cracking hydrogen production catalyst in Example 8. It can be seen from the image that the metal elements are dispersed on the catalyst surface without forming large agglomerates.

[0082] Comparative Example 1

[0083] A silicon-based ammonia cracking hydrogen production catalyst comprises a silicon-based carrier and an active component, wherein the silicon-based carrier is silicon dioxide, the active component is Ni, and the Ni loading amount is 12wt%. The preparation method thereof is similar to that of Example 1 of the present application, and will not be repeated here.

[0084] Comparative Example 2

[0085] A silicon-based ammonia cracking hydrogen production catalyst comprises a silicon-based carrier and an active component, wherein the silicon-based carrier is silicon nitride, the active component is Ru, and the loading amount of Ru is 12wt%. The preparation method thereof is similar to that of Example 1 of the present application, and will not be repeated here.

[0086] Comparative Example 3

[0087] A silicon-based ammonia cracking hydrogen production catalyst comprises a silicon-based carrier and a modification aid, wherein the silicon-based carrier is silicon nitride, the modification aid is Li, and the loading amount of Li is 6 wt %. The preparation method thereof is similar to that of Example 1 of the present application, and will not be described in detail herein.

[0088] The above catalysts are all powders. The silicon-based ammonia cracking hydrogen production catalysts in the above embodiments and comparative examples are tested: the powder to be tested is passed through a 40-60 mesh sieve and pressed into tablets. 1g of the catalyst is loaded into the center of a quartz tube sandwiched with quartz wool. The gas is switched to NH 3 / N 2 The catalyst bed was then adjusted to the target reaction temperature, and the gas composition and content changes were analyzed by the equipped mass spectrometer. The following table lists the NH 3 Conversion rate.

[0089]

[0090] Although the present application has been illustrated and described with specific embodiments, it will be appreciated that many other changes and modifications may be made without departing from the spirit and scope of the present application. Therefore, it is intended that all such changes and modifications within the scope of the present application be included in the appended claims.

Claims

1. A silicon-based ammonia cracking catalyst for hydrogen production, characterized in that: It includes a silicon-based carrier, an active component and a modification aid; The silicon-based carrier includes silicon nitride, silicon-molybdenum powder or SAB-16; The active component includes at least one of Ru, Co, Mo and Fe; The modification aid includes Ir; The loading amount of the active component is 1wt%~10wt%; The loading amount of the modification aid is 0.2wt%~5wt%; The method for preparing the silicon-based ammonia cracking hydrogen production catalyst comprises the following steps: Dissolving the precursor of the active component in water, then adding the precursor of the modifying auxiliary agent, and dispersing by ultrasonication to obtain a first solution; The first solution is mixed with a silicon-based carrier, and the mixture is heated and stirred, followed by drying and calcining to obtain the catalyst; The ultrasonic dispersion time is 0.5~1.5h; the heating and stirring temperature is 60℃~180℃, and the stirring time is 2~10h; the drying temperature is 40~120℃, and the drying time is 10~14h; the calcination atmosphere is an ammonia atmosphere, the calcination temperature is 450~550℃, and the calcination time is 2~6h.

2. Use of the silicon-based ammonia cracking hydrogen production catalyst according to claim 1 in ammonia cracking hydrogen production.

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